Injection devices for setting and dispensing a single or multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.
Injection devices, in particular pen-type injectors have to meet a number of user-specific requirements. For instance, with patient's suffering chronic diseases, such like diabetes, the patient may be physically infirm and may also have impaired vision. Suitable injection devices especially intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easy understandable. Moreover, a dose setting as well as a dose dispensing procedure must be easy to operate and has to be unambiguous.
Typically, such devices comprise a housing or a particular cartridge holder, adapted to receive a cartridge at least partially filled with the medicament to be dispensed. The device further comprises a drive mechanism, usually having a displaceable piston rod which is adapted to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge is displaceable in a distal or dispensing direction and may therefore expel a predefined amount of the medicament via a piercing assembly, which is to be releasably coupled with a distal end section of the housing of the injection device.
The medicament to be dispensed by the injection device is provided and contained in a multi-dose cartridge. Such cartridges typically comprise a vitreous barrel sealed in distal direction by means of a pierceable seal and being further sealed in proximal direction by the piston. With reusable injection devices an empty cartridge is replaceable by a new one. In contrast to that, injection devices of disposable type are to be entirely discarded when the medicament in the cartridge has been completely dispensed or used-up.
Injection devices of pen-injector type typically provide the functionality of setting a dose of variable size and subsequently dispensing or injecting the dose actually set. Such devices typically have a dose size indicator, such like a number sleeve with a sequence of numbers or symbols printed on its outer circumference and being rotatably or helically arranged inside a housing. The housing typically has an aperture or a window through which a particular number of the scale of the number sleeve is visible, thereby representing the size of a dose actually set. Apart from such mechanically implemented dose size indicators there exist also electronically implemented dose size indicators making typically comprising an electronic display.
In general, there exist different configurations, a large variety and different types of dose size indicators. Document US 2011/0270214 A1 for instance discloses a pen-injector with a dosage selector at its proximal end and having a display arranged in an electronic module housing which is arranged in the dosage selector housing. There is further described a memory module for a drug delivery device that provides the user with information in respect of the last delivered dose, hence the amount and time since the last delivery.
The size of a display arranged in a dosage selector is rather limited due to the limited diameter of the dosage selector and the rather filigree and compact overall design of the pen-injector. Especially for elderly patients that may suffer from poor vision it may be rather difficult to correctly read the information provided on such a display. In addition, the rather compact design and dimensions of a dosage selector may impose difficulties also for the correct handling of the dosage selector. Due to its limited size and comparatively small diameter the circumferential gripping area of such dosage selectors is rather limited.